1. Field of the Invention
The present invention generally relates to a method for repairing process-related damage of a dielectric film by cyclic processes, particularly to a method for hydrophobization of a surface of a silicon-containing film by atomic layer deposition (ALD).
2. Description of the Related Art
Dielectric films are indispensable to increasing processing speed of semiconductor devices and lowering power consumption of the devices. Dielectric films are susceptible to damage during their manufacturing processes, thereby increasing dielectric constants and/or leakage currents. Such process-related damage includes damage caused by dry etching and plasma ashing, and washing with chemicals, and physical damage by chemical mechanical planarization (CMP), etc. Particularly, in advanced devices, dielectric films are porous and have low dielectric constant values. Such porous low-k films are highly susceptible to damage during an etching process for patterning or the like, and when the films are damaged, the dielectric constant values increase. In order to recover the dielectric constant values, restoration of the damaged porous surface is necessary. Further, before depositing a barrier metal or the like, pores of the porous surface must be sealed for inhibiting diffusion of the barrier metal. Thus, after the patterning of the dielectric film but before deposition of a barrier metal thereon, restoration and pore-sealing are necessary.
In order to repair such process-related damage of the dielectric films, U.S. Pat. No. 7,851,232 and U.S. Patent Application Publication No. 2011/0159202, for example, disclose repairing damage by UV-excited reaction using a gas containing carbon. However, although damaged surfaces can be restored to a certain degree by the above methods using a hydrocarbon film, restoration is insufficient depending on the degree of damage. Further, a hydrocarbon film can seal pores of the damaged surfaces, but the hydrocarbon film does not have sufficient barrier function as a pore-sealing film against a barrier metal although it can inhibit diffusion of chemicals such as toluene to a certain degree.
Further, a surface of a pore-sealing film or other a silicon-containing film is often subjected to atmospheric exposure, and moisture adsorption occurs on the surface and moisture is diffused through the pore-sealing film and reaches an underlying film such as a low-k film, increasing a dielectric constant of the low-k film.
Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.